It is known that socks are produced with circular machines having one or two needle cylinders, the knitting starting from the elastic hem and finishing at the toe side which is left open to be closed afterwards by suitable seaming or linking machines. More precisely, it is known that after the formation of the necessary ranks (the term rank being used herein to refer to a knit course or stitch course and the term semi rank being used herein to refer to half of a knit course or partial knit course) for--the sock toe, a number of waste ranks (the term waste rank being used herein to refer to a knit course destined to be removed from the knitted article) of a so-called "unthreading" edge (the term unthreading edge being used herein to refer to an edge formed by a number of knit courses destined to be removed from the knitted article) is formed, usually of a single fabric one centimeter high, to avoid ladders during the seaming. According to the type of machine being used, the socks are produced:
a)one after the other. In this case the last rank (last knit course) of the unthreading edge is connected to the first rank of the elastic hem of the next sock through a resistant, smooth and well visible thread, which is worked with a feeding unit other than that for the elastic hem, and is to be manually removed to separate one sock from the other prior to the seaming of the toe; PA0 b) detached from one another. This procedure is used mostly in the single- or two-cylinder circular machines provided with an automatic device for the separation of the manufactured socks.
Afterwards, each sock is to be overturned inside out to allow for seaming on the reverse side of the sock. Then, the toe is closed by removing the waste edge and sewing the last stitches of the last semirank of the back of the foot, together with those of the last rank of the sole of the foot.
However, performing the sewing of the toe of the socks outside the machine which makes them involves increase of time and cost production, mainly as a consequence of the numerous intermediate operations to be carried out between the knitting and the toe seaming, such as the removal and transfer of the socks towards the relevant stocking stores, and the classification thereof on a colour and/or size basis. All this implies, in fact, employing skilled personnel for carrying out and supervising these operations, and the provision of sufficiently wide spaces for siting the machines and for classifying and storing the socks. Moreover, in case of a large number of thus formed socks, the amount of yarn which is lost for the manufacturing of the socks and the subsequent removal of the waste edge, results significantly high and, therefore, the relevant cost will heavily and negatively affect the economic efficiency of the traditional manufacturing plants.
Also known, from document IT 9590-A/87, is a method for the formation of the closed toe of the socks during their manufacturing by a circular machine, including starting the sock with the formation of a tridimensional knit pocket corresponding to the toe. The pocket is formed with double fabric in which two equal edges are united in juxtaposition; proceeding with the formation of the sock foot after having put at work the needles previously made inoperative during the formation of the pocket, so as to hook it up. The above mentioned document also discloses an apparatus for carrying out the method, and with sinkers of half the cylinder of the thus-made-inoperative needles being provided with a crook for engaging the corresponding opposite needle as it is lifted up. A cam acts on the heel of the sinkers, which causes them to be displaced radially to move the head of the relevant opposite needle out of the cylinder. A wheel is provided revolving within the recess of the sinkers, to allow the first semirank of the pocket to be linked to move close to the stitchless needles.
However, this known apparatus does not always ensure that all the needles put at work will engage properly the yarn and, besides, as the linking goes on, that is, as the pocket grows smaller, it does not ensure an equal and uniform knitting.
Also known from the document IT 9465-A/90, is a method to hook-up the toe of the socks by means of the circular machine producing them starting frown the toe. According to this method provision is made for progressively pulling outwards, by a horizontal and gradually decreasing movement, a limited portion of the free semirank of the pocket to be linked, and holding this portion in proximity of the relevant stitchless needles. This is achieved by using the tip of a spring pressing from the inside of the needles cylinder onto the center of the first free semirank of the pocket, in cooperation with two hooks, one being provided with reciprocating horizontal motion and with alternate evolution at the end of every travel, and having the function of progressively linking the region to be linked of the semirank and pulling the latter towards and beyond the needles cylinder. The other is provided with reciprocating vertical motion to retain the semirank region thus treated by the first hook and allow for the link thereof by means of the stitchless needles put at work again.
However, experience has showed that this known working technique does not offer appreciable advantages, both in relation to the quality of the finished product, and to the machine productivity and reliability, and is unable to achieve a sock with rib-stitch elastic hem and unthreading on the inside thereof.